In the Garden:Northern & Central Midwest
April, 2008
Regional Report

Pruning Renews Your Shrubs and You

While many tasks in the garden provide a healthy sense of accomplishment, rejuvenating an overgrown shrub makes you feel like an artist. Transforming a rangy, ugly mockorange or dogwood into a thing of beauty is easier than you think.

Shrubs that benefit from regular renewal or rejuvenation pruning include forsythia, honeysuckle, mockorange, privet, redtwig and yellowtwig dogwood, shrub roses, spirea, and viburnum. The process typically involves removing one-fifth to one-third of the oldest and largest stems at ground level. Cutting the larger stems encourages vigorous growth from the ground, making the shrub full from the bottom up. Selective pruning also improves the shrub's flowering capacity by allowing more light to reach the interior of the plant. Old shrubs that haven't been regularly pruned may need complete rejuvenation, a three-year process, while young plants only require light pruning each year.

Although overgrown shrubs detract from a landscape, it's also important to consider how the landscape will look while waiting the two or three years it takes a plant to recover from severe pruning. It's also important not to do renewal pruning when a shrub is unhealthy or stressed. Shrubs may be particularly stressed after a dry summer, so spend the autumn bringing the shrub back to vigor and then prune the following early spring.

Tools
One of the most important aspects of renewal pruning is using the right tools. A pair of good pruning shears and a sharp pruning saw are as important as using the correct process. Jagged cuts and frustration from trying to make a tool do something it's not intended to do can ruin the outcome.

Technique
First, assess a shrub's shape and growth tendencies. Since you have to work with what is there, study the shrub carefully. Is it upright or spreading? Do more of the branches come from the ground or from forks above the ground?

Begin pruning by removing any diseased or damaged branches. Next, select up to one-third of the oldest stems and cut them at ground level with long-handled loppers or a pruning saw. Try to remove stems carefully from all sides of the shrub to keep it somewhat symmetrical.

Remember to periodically step back and look at the shape of the entire plant as you are pruning. With an old shrub, it's tempting to jump in and start cutting, but caution and patience will produce a better plant. It is important not to remove any more than one-third of the shrub at a time in order to leave enough leaf surface to provide food for the plant.

After removing the large stems, prune out any crossing branches, open the crown to more sunlight by thinning side branches, and shorten other stems to produce a pleasing shape. Step back one last time and do any final shaping. Then the job is finished for this year. For the next two years, follow the same process, removing another third of the old branches and shaping the plant. After the third year, remove only one-fourth of the branches each year.